Novel Controlled-Release Breakers for High-Temperature Fracturing

Abstract

Various types of breaker systems are used for viscosity degradation of fluids in fracture stimulation operations. Achieving improved fracture conductivity is one of the key advantages of using effective breaker systems, but there could be an increased risk of poor proppant placement and premature screenouts resulting from early viscosity reductions as the fluid is exposed to temperature. To resolve this issue, a controlled release of the breaker over a period of time is very desirable.This paper highlights the controlled release of encapsulated oxidizers and chelating types of breakers that are effective in bottomhole static temperatures (BHSTs) up to 275°F. Oxidizers without encapsulation begin to decompose fluids at low to moderate temperature, which can lead to a rapid decrease in gel viscosity before completion of the fracturing operation. Neat chelating breakers can absorb the crosslinker rapidly; thus, little to no crosslinking action would be present, even at moderate temperatures. A newly developed encapsulant makes oxidizers and chelating agents viable for reducing the crosslinked viscosity gradually with temperature.The new encapsulant is a blend of selected polymers that release the active breaker through diffusion. It is possible to optimize the release rate of a breaker by simply adjusting its ratio in a polymer blend. The controlled release of a breaker through an encapsulant was evaluated at 200°F under static conditions. The dynamic rheology of fracturing fluids was also studied as a function of encapsulated breaker concentration in temperatures up to 275°F. The results derived from this investigation are of significant importance to the oilfield industry.

Improving Fracture Conductivity by Developing and Optimizing Channels within the Fracture Geometry: CFD Study

“…Enhancing crosslinker chemistry Ainley et al 1993, Putzig and St. Clair 2007, Sun and Qu 2011, and Legemah et al 2013 Enhancing breaker chemistry Brannon 1994, Sarwar et al 2011, Gunawan et al 2012, and Patil et al 2013 Fracture fluid additives Bang et al 2008, andKim et al 2015 Foamed fluids Hutchins and Miller 2005, Gupta et al 2005, Chen et al 2005, Friehauf and Sharma 2009, and Gupta and Carman 2011 Viscoelastic surfactant systems Samuel et al 1999, Gomaa et al 2011, and Gomaa et al 2015 Polymer chemistry Cramer et al 2004, and Gomaa et al 2014Proppant Technology Brannon et al 2004 These improvements contributed incrementally toward the goal of attaining the maximum theoretical conductivity that can be achieved in a homogeneous proppant pack.…”

Application of Hydrogels and Hydrocarbon-Based Gels in Oil Production Processes and Well Drilling

“…Moreover, the structure of these compounds justifies the possible temperature ranges of application. Destructors in the polymer shell are used to slow down the action at temperatures above 70–80 °C [ 41 ]. The action of oxidative destructors is based on the generation of free radicals that interact with the polymer chain and provoke its rupture to lower molecular weight components [ 42 , 43 ].…”

A review of fracturing fluid systems used for hydraulic fracturing of oil and gas wells

“…Delayed release systems capable of delaying the activity of breakers or crosslinking of guar during the injection are another important focus of the oil and gas industry. 34,35,69,70 Slickwater Fluids The current focus of the industry is on the following items: Development of a system that can use less or no water, in order to address the concerns regarding high water volumes being used and also other concerns regarding near fracture damage. Development of gas-based fracturing systems and efficient fluid loss additives for smaller pore size formations are currently being pursued for this purpose.…”

“…Moreover, the industry is focused on development of environmentally‐ and equipment‐friendly breakers that can be applied at high temperatures and extremely low or high pH conditions. Delayed release systems capable of delaying the activity of breakers or crosslinking of guar during the injection are another important focus of the oil and gas industry …”